1. Field of the Invention
The present invention relates in general to a wire-feeding device for correctly supplying an Au-wire in a bonding process.
2. Description of the Related Art:
Referring to FIG. 1, a conventional wire-feeding device includes an Au-wire supply 17, a driver 16, a buffer tension 11 and a blow tension 12. The wire supply 17 is actuated by the driver 16 to supply an Au-wire wrapped round the wire supply 17. Furthermore, the buffer tension 11 has a body 111 and two pulleys 112, 112' provided on both sides of the body 111. The Au-wire is stretched over the pulleys 112, 112' and connected to the blow tension 12.
In operation, the Au-wire is laterally blown by the buffer tension 11 and meanwhile axially blown by the blow tension 12, as indicated by the arrows in FIG. 1, so that a section 13 of the Au-wire between the pulleys 112, 112' is bent (hereinafter the bent section of the Au-wire is called the "wire loop"). A sensor 14 is provided beside the wire loop 13 to detect the wire loop 13 and send a signal to the driver 16 of the Au-wire supply 17 through an amplifier 15, in order to determine if supplying the Au-wire is required.
The Au-wire is expended during the bonding process. Accordingly, the wire loop 13 contracts in size until the sensor 14 fails to detect the wire loop 13. When the sensor 14 fails to detect the wire loop 13, an indicating lamp 18 of the amplifier 15 is extinguished, the driver 16 of the wire supply 17 is actuated and the wire supply 17 starts to supply the Au-wire. By this arrangement, a minimum size of the wire loop 13 can be maintained so that the bonding process can proceed normally.
However, if the air flow generated by the buffer tension 11 and the air flow generated by the blow tension 12 do not interact well, then the wire loop 13 will vertically shake. As shown in FIG. 2, it is possible for the shaking wire loop 13 to move outside the region which the sensor 14 detects. When the sensor 14 fails to detect the wire loop 13, the indicating lamp 18 of the amplifier 15 is extinguished, the driver 16 of the wire supply 17 is actuated and the wire supply 17 starts to supply the Au-wire. The wire loop 13 becomes longer and longer due to the continuous supply of the Au-wire. Finally, the bonding products have failures such as open shot, stitch peel off, wire break, abnormal loop and so on.